Climate Change: The Move to Action (AOSS 480 // NRE 501) Richard B. Rood Space Research Building (North Campus) Winter 2008 January 22, 2008

Class News A ctools site for all –AOSS W08 This is the official repository for lectures Class Web Site and Wiki –Climate Change: The Move to ActionClimate Change: The Move to Action –Winter 2008 TermWinter 2008 Term Thursday I’m going to ask: “Have you been thinking about projects?”

Class News: Get the registration right If you signed up for AOSS 480 or NRE 501 (Climate Change: The Move to Action), and that is what you wanted to do, then that is all good. If you signed up for AOSS 480, but want the QuikClimate course on the physical climate system (AOSS 605), then you should change over to 605. This course has been “approved” by SNRE as permanent! Hence, there may be a 501 number change. –Stay tuned, if you need to do anything. If you signed up for AOSS 605 or AOSS 480 and have decided that you want to take both, then my advice would be to register for both.

Readings on Local Servers Assigned –IPCC Working Group I: Summary for Policy MakersIPCC Working Group I: Summary for Policy Makers Of Interest –Lean: Living with a Variable SunLean: Living with a Variable Sun –Doney: Ocean AcidificationDoney: Ocean Acidification

Outline of Lecture Greenhouse effect Radiative Balance of the Earth Earth’s Climate System –Atmosphere Clouds –Oceans –Land –Ice (Cryosphere)

The Conservation Principle The idea that some basic quantities are conserved. –Energy obeys a conservation equation. –Carbon dioxide obeys a conservation equation Analysis of the conservation equation is a counting problem – the calculation of a budget. –The amount that you have is equal to the amount that you started with, plus the amount that you acquired (income or production), minus the amount that you got rid of (expense or loss)

Basic mathematical form of the conservation principle. HEATING COOLING Proportional to how hot it is.

If the energy from Earth is in balance Then T (temperature is not changing) This is the essence of the global warming problem. What is the balance of heating and cooling?

Look at the Earth from Space

Conservation principle Energy from the Sun Energy emitted by Earth (proportional to T) Earth at a certain temperature, T Stable Temperature of Earth could change from how much energy (H) comes from the sun, or by changing how much we emit, related to.

But the Earth’s surface temperature is observed to be, on average, about 15 C (~59 F). The Greenhouse Effect SUN Earth Based on conservation of energy: If the Earth did NOT have an atmosphere, then, the temperature at the surface of the Earth would be about -18 C ( ~ 0 F). This temperature, which is higher than expected from simple conservation of energy, is due to the atmosphere. The atmosphere distributes the energy vertically; making the surface warmer, and the upper atmosphere cooler, which maintains energy conservation. This greenhouse effect is well known.

But the Earth’s surface temperature is observed to be, on average, about 15 C (~59 F). The Greenhouse Effect SUN Earth Based on conservation of energy: If the Earth did NOT have an atmosphere, then, the temperature at the surface of the Earth would be about -18 C ( ~ 0 F). This temperature, which is higher than expected from simple conservation of energy, is due to the atmosphere. The atmosphere distributes the energy vertically; making the surface warmer, and the upper atmosphere cooler, which maintains energy conservation. We are making the atmosphere “thicker.” This greenhouse effect in not controversial.

Energy conservation of Earth If we change the heating or the cooling rate then we will change the equilibrium. Will ultimately reach a new equilibrium. Changing a greenhouse gas changes this

Energy conservation for Earth We reach a new equilibrium Changes in orbit or solar energy changes this Can we measure the imbalance when the Earth is not in equilibrium?

Some aspects of the greenhouse effect Greenhouse warming is part of the Earth’s natural climate system. –It’s like a blanket – it holds heat near the surface for a while before it returns to space. –We have been calculating greenhouse warming for a couple of centuries now. Water is the dominant greenhouse gas. Carbon dioxide is a natural greenhouse gas. –We are adding at the margin – adding some blankets Or perhaps closing the window that is cracked open. N 2 0, CH 4, CFCs,... also important. –But in much smaller quantities.

Something of a summary We know that CO 2 in the atmosphere holds thermal energy close to the surface. Hence, more CO 2 will increase surface temperature. –Upper atmosphere will cool. –How will the Earth respond? Is there any reason for Earth to respond to maintain the same average surface temperature? Why those big oscillations in the past? –They are linked to solar variability. –Release and capture of CO 2 by ocean plausibly amplifies the solar oscillation. Solubility pump Biological pump What about the relation between CO 2 and T in the last 1000 years? –Look to T (temperature) variability forced by factors other than CO 2 Volcanic Activity Solar variability CO 2 increase Radiative forcing other than CO 2 ? –Other greenhouse gases –Aerosols (particulates in the atmosphere)

Radiative Balance of The Earth Over some suitable time period, say a year, maybe ten years, if the Earth’s temperature is stable then the amount of energy that comes into the Earth must equal the amount of energy that leaves the Earth. –Energy comes into the Earth from solar radiation. –Energy leaves the Earth by terrestrial (mostly infrared) radiation to space. (Think about your car or house in the summer.)

Radiation Balance Figure

Let’s build up this picture Follow the energy through the Earth’s climate. As we go into the climate we will see that energy is transferred around. –From out in space we could reduce it to just some effective temperature, but on Earth we have to worry about transfer of energy between thermal energy and motion of wind and water.

But the Earth’s surface temperature is observed to be, on average, about 15 C (~59 F). The sun-earth system (What is the balance at the surface of Earth?) SUN Earth Based on conservation of energy: If the Earth did NOT have an atmosphere, then, the temperature at the surface of the Earth would be about -18 C ( ~ 0 F). Welcome Back Radiative Balance. This is conservation of energy, which is present in electromagnetic radiation.

Building the Radiative Balance What happens to the energy coming from the Sun? Energy is coming from the sun. Two things can happen at the surface. In can be: Reflected Top of Atmosphere / Edge of Space Or Absorbed

Building the Radiative Balance What happens to the energy coming from the Sun? We also have the atmosphere. Like the surface, the atmosphere can: Top of Atmosphere / Edge of Space Reflect or Absorb

Building the Radiative Balance What happens to the energy coming from the Sun? In the atmosphere, there are clouds which : Top of Atmosphere / Edge of Space Reflect a lot Absorb some

Building the Radiative Balance What happens to the energy coming from the Sun? For convenience “hide” the sunbeam and reflected solar over in “RS” Top of Atmosphere / Edge of Space RS

Building the Radiative Balance What happens to the energy coming from the Sun? Consider only the energy that has been absorbed. What happens to it? Top of Atmosphere / Edge of Space RS

Building the Radiative Balance Conversion to terrestrial thermal energy. 1) It is converted from solar radiative energy to terrestrial thermal energy. (Like a transfer between accounts) Top of Atmosphere / Edge of Space RS

Building the Radiative Balance Redistribution by atmosphere, ocean, etc. 2) It is redistributed by the atmosphere, ocean, land, ice, life. (Another transfer between accounts) Top of Atmosphere / Edge of Space RS

Building the Radiative Balance Terrestrial energy is converted/partitioned into three sorts SURFACE 3) Terrestrial energy ends up in three reservoirs (Yet another transfer ) Top of Atmosphere / Edge of Space ATMOSPHERE CLOUD RS WARM AIR (THERMALS) PHASE TRANSITION OF WATER (LATENT HEAT) RADIATIVE ENERGY (infrared) It takes heat to Turn ice to water And water to “steam;” that is, vapor

Building the Radiative Balance Which is transmitted from surface to atmosphere SURFACE 3) Terrestrial energy ends up in three reservoirs Top of Atmosphere / Edge of Space ATMOSPHERE CLOUD RS (THERMALS)(LATENT HEAT) (infrared) CLOUD

Building the Radiative Balance And then the infrared radiation gets complicated SURFACE Top of Atmosphere / Edge of Space ATMOSPHERE CLOUD RS (THERMALS)(LATENT HEAT) (infrared) CLOUD 1) Some goes straight to space 2) Some is absorbed by atmosphere and re-emitted downwards 3) Some is absorbed by clouds and re-emitted downwards 4) Some is absorbed by clouds and atmosphere and re-emitted upwards

Put it all together and this what you have got. The radiative balance

Thinking about the greenhouse A thought experiment of a simple system. SURFACE Top of Atmosphere / Edge of Space ATMOSPHERE (infrared) 1)Let’s think JUST about the infrared radiation Forget about clouds for a while 2) More energy is held down here because of the atmosphere It is “warmer” 3) Less energy is up here because it is being held near the surface. It is “cooler”

Thinking about the greenhouse A thought experiment of a simple system. SURFACE Top of Atmosphere / Edge of Space ATMOSPHERE (infrared) T effective 1)Remember we had this old idea of a temperature the Earth would have with no atmosphere. This was ~0 F. Call it the effective temperature. Let’s imagine this at some atmospheric height. 2) Down here it is warmer than T effective T > T effective 3) Up here it is cooler than T effective T < T effective

Thinking about the greenhouse Why does it get cooler up high? SURFACE Top of Atmosphere / Edge of Space ATMOSPHERE (infrared) 1) If we add more atmosphere, make it thicker, then 2) The part coming down gets a little larger. It gets warmer still. 3) The part going to space gets a little smaller It gets cooler still. The real problem is complicated by clouds, ozone, ….

So what matters? Things that change reflection Things that change absorption Changes in the sun If something can transport energy DOWN from the surface. THIS IS WHAT WE ARE DOING

CLOUD-WORLD The Earth System ATMOSPHERE LAND OCEAN ICE (cryosphere) SUN

CLOUD-WORLD The Earth System ATMOSPHERE LAND OCEAN ICE (cryosphere) SUN Where absorption is important

CLOUD-WORLD The Earth System ATMOSPHERE LAND OCEAN ICE (cryosphere) SUN Where reflection is important

CLOUD-WORLD The Earth System ATMOSPHERE LAND OCEAN ICE (cryosphere) SUN Solar Variability

CLOUD-WORLD The Earth System ATMOSPHERE LAND OCEAN ICE (cryosphere) SUN Possibility of transport of energy down from the surface

From Warren Washington

Transport of heat poleward by atmosphere and oceans This is an important part of the climate system One could stand back far enough in space, average over time, and perhaps average this away. This is, however, weather... and weather is how we feel the climate day to day –It is likely to change because we are changing the distribution of average heating

While Building the Radiative Balance Figure Redistribution by atmosphere, ocean, etc. SURFACE 2) Then it is redistributed by the atmosphere, ocean, land, ice, life. Top of Atmosphere / Edge of Space ATMOSPHERE CLOUD RS 1) The absorbed solar energy is converted to terrestrial thermal energy.

Another important consideration. Latitudinal dependence of heating and cooling SURFACE ATMOSPHERE CLOUD Equator (On average heating) North Pole (Cooling) South Pole (Cooling) Because of tilt of Earth, Solar Radiation is absorbed preferentially at the Equator (low latitudes). Top of Atmosphere / Edge of Space After the redistribution of energy, the emission of infrared radiation from the Earth is ~ equal from all latitudes.

Transfer of heat north and south is an important element of the climate at the Earth’s surface. Redistribution by atmosphere, ocean, etc. SURFACE Top of Atmosphere / Edge of Space ATMOSPHERE CLOUD heat is moved to poles cool is moved towards equator This is a transfer. Both ocean and atmosphere are important! This predisposition for parts of the globe to be warm and parts of the globe to be cold means that measuring global warming is difficult. Some parts of the world could, in fact, get cooler because this warm and cool pattern could be changed.

Hurricanes and heat: Sea Surface Temperature

Weather Moves Heat from Tropics to the Poles HURRICANES

Mid-latitude cyclones & Heat

CLOUD-WORLD The Earth System ATMOSPHERE LAND OCEAN ICE (cryosphere) SUN

CLOUD-WORLD Earth System: Sun ATMOSPHERE LANDOCEAN ICE (cryosphere) SUN Lean, J., Physics Today, 2005 SUN: Source of energy Generally viewed as stable Variability does have discernable signal on Earth Impact slow and small relative to other changes Lean: Living with a Variable Sun

CLOUD-WORLD Earth System: Atmosphere ATMOSPHERE Change CO2 Here LANDOCEAN ICE (cryosphere) SUN The Atmosphere: Where CO 2 is increasing from our emissions Absorption and reflection of radiative energy Transport of heat between equator and pole Weather: Determines temperature and rain What are the most important greenhouse gasses? Water (H 2 O) Carbon Dioxide (CO 2 ) Methane (CH 4 )

Cloudy Earth

CLOUD-WORLD Earth System: Cloud World ATMOSPHERE LANDOCEAN ICE (cryosphere) SUN Cloud World: Very important to reflection of solar radiation Very important to absorption of infrared radiation Acts like a greenhouse gas Precipitation, latent heat Most uncertain part of the climate system. Reflecting Solar Cools Largest reflector Absorbing infrared Heats

CLOUD-WORLD Earth System: Land ATMOSPHERE LAND Change Land Use Here OCEAN ICE (cryosphere) SUN Land: Absorption of solar radiation Reflection of solar radiation Absorption and emission of infrared radiation Plant and animal life Impacts H 2 O, CO 2 and CH 4 Storage of moisture in soil CO 2 and CH 4 in permafrost Land where consequences are, first and foremost, realized for people. What happens to atmospheric composition if permafrost thaws? Can we store CO 2 in plants? Adaptability and sustainability?

CLOUD-WORLD Earth System: Ocean ATMOSPHERE LAND OCEAN ICE (cryosphere) SUN Ocean: Absorption of solar radiation Takes CO 2 out of the atmosphere Plant and animal life Impacts CO 2 and CH 4 Takes heat out away from surface Transport of heat between equator and pole Weather regimes: Temperature and rain What will the ocean really do? Will it absorb all of our extra CO 2 ? Will it move heat into the sub-surface ocean? Changes in circulation? Does it buy us time? Does this ruin the ocean? Acidification Doney: Ocean Acidification

Do you know about the Younger Dryas? Lamont-Doherty: Abrupt Climate Change

Bubbles of gas trapped in layers of ice give a measure of temperature and carbon dioxide 350,000 years of Surface Temperature and Carbon Dioxide (CO 2 ) at Vostok, Antarctica ice cores  During this period, temperature and CO 2 are closely related to each other  It’s been about 20,000 years since the end of the last ice age

Younger Dryas POSSIBLE EVIDENCE OF CHANGE IN OCEAN CIRCULATION WHAT DOES THIS MEAN?

CLOUD-WORLD Earth System: Ice ATMOSPHERE LANDOCEAN ICE (cryosphere) SUN ICE: Very important to reflection of solar radiation Holds a lot of water (sea-level rise) Insulates ocean from atmosphere (sea-ice) Ice impacts both radiative balance and water – oceans and water resources on land.. Large “local” effects at pole. Large global effects through ocean circulation and permafrost melting. Might change very quickly.

The Earth System: ICE (Think a little more about ice) non-polar glaciers and snow polar glaciers (Greenland) (Antarctica) sea-ice Impacts regional water supply, agriculture, etc. Solar reflection, Ocean density, Sea-level rise Solar reflection, Ocean-atmosphere heat exchange (Tour of the cryosphere, Goddard Scientific Visualization Studio)

The Cryosphere TOUR OF CRYOSPHERE: MAIN NASA SITETOUR OF CRYOSPHERE: MAIN NASA SITE